Specific embodiments of the present invention will be described by taking a Digital Video Broadcasting-Satellite 2 (DVB-S2) as an example of a satellite broadcasting system. As the boundary between broadcasting and communication becomes obscure and bi-directional services are available recently, it is required to develop broadband services and reliable transmission services. Thus, satellite broadcasting systems which require high transmission capacity with given bandwidths and signal power adopt adaptive modulation and coding methods.
Particularly, the European standard for digital video satellite broadcasting, i.e., DVB-S2, utilizes adaptive modulation and coding methods which select optimal modulation scheme and coding rate adaptive to channel conditions. The use of the adaptive modulation and coding methods allows receivers of a satellite communication system to control links adaptively to propagation conditions and thereby acquire transmission capacity up to about 100 to 200%.
However, each receiver of the satellite communication system adopting the transmission method essentially requires a frame structure detection process for identifying a varied transmission frame and a frame sync position detection process for detecting the start point of a frame.
Generally, the performance in the frame sync detection process and the frame structure detection process that are carried right after symbol synchronization in the initial synchronization mode are significant parameters that become basic assumption for acquiring performance required in the entire system.
One of the methods for detecting frame sync is to estimate the start point of a frame by deciding reliability of correlation analysis values after correlation analysis. According to the method, correlation values are all stored in a method applicable to the decision of reliability of correlation analysis and the maximum value among them is used. F. W. Sun, Y. Jiang and L. N. Lee disclose a method for detecting a frame based on a maximum value in an article entitled “Frame Synchronization and Pilot Structure for Second Generation DVB via Satellites,” International Journal of Satellite Communications and Networking, Vol. 22, pp. 319-339, 2004.
According to the article, frame sync is detected based on a maximum value of correlation analysis values within a predetermined section of a DVB-S2 frame structure, and the frame structure and frame sync position are detected through Reed Muller (64.7) decoding of physical layer signaling code (PLSC) bits.
However, the conventional frame detection method requires an additional process for correcting frequency and phase errors in the PLSC decoding. In addition, a process of detecting accurate position information of a frame should precede the PLSC decoding. Therefore, there is a limit in applying the conventional frame detection method to an environment with frequency errors.
Another frame detection method for transmission frames having variable frame length is disclosed in Korean Patent Application No. 10-1999-7000294 by NTT Docomo, entitled “Transmission Method, Device and Receipt Device of Variable Length Frame.”
According to the frame detection method of the technology disclosed in the above patent application, frames with variable length should be segmented based on predetermined segmentation rules to be transmitted in the form of multiple coded streams and added with a sync flag. Then, frame structure and frame sync position of transmitted frames are detected based on flags upon reception. Therefore, the technology cannot be applied to frames with fixed sync words, such as frames of a DVB-S2 system.